Temperature effect on the electrical properties of undoped NiO thin films

被引:71
作者
Hakim, A. [1 ]
Hossain, J. [1 ]
Khan, K. A. [1 ]
机构
[1] Rajshahi Univ, Dept Appl Phys & Elect Engn, Rajshahi 6205, Bangladesh
关键词
NiO thin films; E-beam technique; Temperature dependence of resistivity; Size effect; Activation energy; Thermoelectric power; NICKEL-OXIDE; ELECTROCHROMIC PROPERTIES; TUNGSTEN-OXIDE; TRANSPARENT;
D O I
10.1016/j.renene.2009.05.014
中图分类号
X [环境科学、安全科学];
学科分类号
08 ; 0830 ;
摘要
Undoped NiO thin films have been prepared onto glass substrate by e-beam evaporation of the element Ni in vacuum at similar to 2 x 10(-4) Pa. The as-deposited Ni films were then oxidized in air by heating about 2 h at a temperature of 470 K and then the oxidized Ni films are turned into NiO thin films. From the deposition time and film thickness after annealing in air, an effective deposition rate of NiO thin films was about 6.67 nms(-1). X-ray diffraction (XRD) study shows the NiO films are amorphous in nature. SEM studies of the surface morphology of NiO films exhibit a smooth and homogeneous growth on the entire surface. The elemental composition of NiO films is estimated by Energy Dispersive Analysis of X-rays (EDAX) method. The effects of temperature on the electrical properties of NiO thin films were studied in details. The heating and cooling cycles of the samples are reversible in the investigated temperature range after successive heat-treatment in air. Thickness dependence of conductivity is well in conformity with the Fuchs-Sondheimer theory. Temperature dependence of electrical conductivity shows a semiconducting behavior with activation energy, The thickness dependence of activation energy as well as thermopower studies was done within 293-473 K temperature range, respectively. Thermopower study indicates the NiO films a P-type semiconductor. Optical study in the wavelength range 0.3 < lambda < 1.2 mu m range exhibits a high transmittance in the visible as well as in the near infra-red. Calculation from the optical data, the NiO sample exhibits a band gap at 3.11 eV, which does agree well with earlier reported values. These studies may be of importance for the application of this material in energy efficient surface coating devices. (C) 2009 Elsevier Ltd. All rights reserved.
引用
收藏
页码:2625 / 2629
页数:5
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